This invention relates to a high speed board trimmer and in particular to a trimmer having upstream near-end pre-trimming saws.
Much effort in the past has focused on improving lumber sawing methods to optimize board production and reduce wastage. For example, after a cant has been sawn into boards, the boards may be left with wane, defects, weakened areas or other imperfections at the ends of the boards which must be trimmed off. On high speed transfer it has proven difficult in the prior art to accurately trim such boards.
In the prior art it is known to employ trimmers having a single laterally spaced array of drop-down saws, for example on two foot centers, where each of the drop-down saws in the array is equally spaced from adjacent saws and is individually selectively actuable. The trimmer may be immediately downstream of a fixed or active fence for prepositioning a board relative to the array of saws for approximately optimized trimming of defects from ends of the board. In the prior art it is also know to laterally shift the array of drop-down saws in the trimmer, for example as a substitute for, or in addition to, the use of, an active fence for optimizing positioning of the board relative to the saws prior to trimming by one or more of the drop-down saws. One problem in using drop-down saws in a high speed transfer has been the mechanical limitations on how quickly a drop-down saw may be actuated so as to drop into, and to be elevated from, the flow path of boards on the board conveyor.
In the prior art Applicant is also aware of U.S. Pat. No. 5,142,955 which issued Sep. 1, 1992 to Hale for a Lumber Cutter for Removing End Defects and Sawing to Desired Lengths in which is disclosed a root end trim saw extending over a root end edge of a plurality of chain belt conveyers transverse to a longitudinal dimension of boards on the conveyer, the root end trim saw including a motor driven rotating circular saw blade articulated to move down into, or up out of the path of lumber pieces on the conveyer and also slidably mounted to be moved over a range of approximately 24 inches in one half inch increments to thereby cut away a defective portion of a lumber piece identified by a scanner. In applicant""s view, because the saw of Hale has to be both articulated vertically and translated laterally, difficulty would be encountered in timely pre-positioning the saw and cutting lumber accurately in a high speed transfer of boards downstream into a trimmer.
Consequently, it is one object of the present invention to provide a pre-trimmer circular saw which may be rapidly pre-positioned for a particular board in the board flow to accurately pre-trim a near-end of the board as it is translated downstream on a trimmer in-feed transfer and then retracted out of the flow path or re-positioned for a subsequent board so as to allow trimming of the boards in the trimmer with improved accuracy.
A further objective is to provide a method of trimming the near-end of a scanned board by the use of a board elevator to elevate each board so as to engage a pre-trim saw as necessary for optimized trimming by a downstream trimmer.
The lumber trimmer with pre-trimmer saws of the present invention is mounted within a green or dry lumber line having an upstream scanner and upstream transverse ending rolls. The scanner scans each board and the scanned board data is processed by an optimizer to provide an optimized trimming solution for each board. The optimizer determines an optimum trimmed length and relative position trimmed board segment relative to each board so as to recover the highest value length of lumber, based, for example, on one or two foot increments between trimmer saws, which is practicable to retrieve within a xe2x80x9cgood woodxe2x80x9d boundary established by the optimizer. The optimizer then calculates a lateral translation distance for an upstream pre-trimmer saw located between the scanner and a downstream multi-saw drop-saw trimmer to allow accurate recovery of xe2x80x9cgood woodxe2x80x9d by the multi-saw trimmer. The ending rolls, or other board ending means such as in-line xe2x80x9cskatexe2x80x9d wheels end boards transversely across a flow path so as to end the near ends of the boards against a fixed fence positioned at the near side of an upstream end of the multi-saw trimmer. The fixed fence is of sufficient length to allow for dampening of lumber bounce-back. The pre-trimmer saw or plurality of such saws comprise one or more selectively laterally positionable near-end saws mounted at the near side of said flow path, for example upstream of the fence and upstream of the trimmer. The pre-trimmer saws are positioned by selectively actuable actuators so as to position the saws in a direction transverse to the lumber flow path and parallel to transversely aligned boards on lugged transfer chains translating the boards along the flow path. The boards may be individually elevated on a board elevator, so as to be near-end trimmed by the pre-trimmer saws. The board elevator may be, for example, a plurality of lugged discs or wheels in laterally spaced array beneath the pre-trimmer saws, spaced transversely across said flow path. Other board elevators such as speed-up chains, or belts, or slides would work. This allows for a higher board transfer rate than for example might be obtained using the Hale device which vertically actuates saws into and out of the board flow path.
In summary the board trimmer having pre-trimmer saws of the present invention includes a selectively translatable upstream first pre-trimmer saw mounted on a near-side of a board flow path of a board transfer, upstream of a downstream multi-saw board trimmer. The pre-trimmer saw is selectively translatable by an actuator for translation linearly parallel to a near-side ended board on the board transfer. The pre-trimmer saw is perpendicular to the board when on the board transfer. A board elevator may be mounted below the board flow path and the pre-trimmer saw for elevating the board from a sequence of single boards from the board transfer into sawing engagement with the pre-trimmer saw once the pre-trimmer saw has been pre-positioned by the actuator into an optimized cutting path. Trimming of the board in the flow path is done according to an optimized solution for trimming the board. The board may be optimally trimmed by a combination of trimming a first waste portion from a near-end of the board by the first pre-trimmer saw and by trimming a second waste portion from either or both of the near-end and a far end of the board by the downstream multi-saw trimmer.
In one embodiment the board elevator is a rotatable disc, or array of such discs, having mounted thereon a means for carrying the board fixed, i.e. immobile, relative to the disc as the disc rotates in a direction corresponding to the flow path and the board is carried over the disc, where the disc is parallel to the pre-trimmer saw and rotatably mounted below the board transfer so that only an upper periphery of the disc extends above the board transfer. The upper periphery rotates in the direction corresponding to the flow path. In the case where the board elevator is an array of the rotatable discs, the array of the rotatable discs extends across the flow path, parallel to a board on the board transfer.
A selectively translatable second pre-trimmer saw may be mounted parallel to, and downstream of, the first pre-trimmer saw. The second pre-trimmer saw is selectively translatable parallel to the selective translation of the first pre-trimmer saw. The board elevator may also be below the second pre-trimmer saw. Thus in one embodiment the board elevator may include both a first rotatable disc corresponding to the first pre-trimmer saw and a second rotatable disc corresponding to the second pre-trimmer saw. The first and second rotatable discs may both have mounted thereon a means for carrying the board fixed relative to the first or second rotatable discs respectively. The discs may be parallel to the pre-trimmer saws and rotatably mounted below the board transfer so that only an upper periphery of the discs extend above the board transfer, the upper periphery of both discs rotating in the direction corresponding to the flow path.
The board elevator may also be a first array of spaced-apart rotatable discs and a second downstream array of spaced-apart rotatable discs, the first and second arrays corresponding to the first and second pre-trimmer saws for elevating a board into the first or second pre-trimmer saws respectively. The first and second arrays may extend across the flow path, parallel to each other and to a board when on the board transfer.
The means for carrying a board fixed relative to a disc may be at least one lug or protrusion (collectively referred to as a lug) extending radially outwardly of the disc so as to extend upwardly from the upper periphery of the disc during rotation of the disc. The lug rotates on the disc into engagement with an upstream side of the board as the board is carried over the disc. The at least one lug may be a pair of oppositely disposed lugs.
A selectively laterally translatable ending saw may be provided downstream of the first pre-trimmer saw and mounted on the near-side of the board flow path to act in combination with the pre-trimmer saw or saws. The ending saw is selectively actuable by an ending saw actuator to extend the ending saw into the flow path to trim a selectively optimized end portion from the board as the board passes towards, through or away from the multi-saw saw trimmer. The ending saw cooperates with the pre-trimmer saw or saws to allow for optimized trimming of a far-end waste portion, opposite to the near-end waste portion, from the board during selective sawing by saws of the multi-saw board trimmer, wherein the board is a near-side ended board. The board is near-side ended between the pre-trimmer saw or saws and the ending saw.
A board is first ended by a first board ending means mounted upstream of the first pre-trimmer saw. A second board ending means is mounted between the pre-trimmer saw or saws and the ending saw so as to cooperate with boards in the flow path, to near-side end them before they engage the ending saw.